22 HOW BACTERIA ARE NAMED AND IDENTIFIED 



is designated as the type genus. In general the name of the family is formed from 

 the name of the type genus by affixing the suffix -aceac to the stem of the generic 

 name. The word is plural. Among bacterial families commonly recognized are 

 Bacillaceae, named from its type genus, Bacillus^ Pseudomonadaceae from Pseu- 

 domonas, Spirochaetaceae from Spirochaeia, Actinomycetaceae from Actinomyces 

 and Spirillaceae from Spirillum. 



(4) Order. An order is a group of related families. It is usually named by 

 substituting the suffix -ales for -aceae in the name of the type family. Among 

 ordinal names that have been used in bacteriology are Actinomijcetales, Spiro- 

 chaetales, Myxohacterales. 



(5) Class. A class is a group of related orders. In this treatise the bacteria 

 are treated as constituting the class Schizomycetes in Division I., Protophyta, of 

 the plant kingdom. 



(6) Other categories. Other categories or ranks of names are used for higher 

 groups. Sometimes families are divided into sub-families, these into tribes, these 

 into subtribes, and these finally into genera. 



How to identify an organism by name. One of the purposes of this Man- 

 ual OF Determinative Bacteriology, as noted previously, is to facilitate the 

 finding of the correct scientific name of a bacterium. It is well, however, to note 

 some of the reasons why this result, the identification of an unknown culture, 

 may not eventuate. Among these the following may be listed: 



(1) The unknown organism awaiting identification b}^ the investigator may 

 possibly be one which has never been named; or, if named, perhaps was inade- 

 quately described. Of course it will not be listed in the Manual. Little effort 

 on the part of bacteriologists has been devoted to describing or naming bacteria 

 except as they have been found to have some economic significance or to possess 

 some striking or unusual characteristics. There are quite probably many times 

 as many species of unknown bacteria as have been described and named. Such 

 unknown species are all about us. It is not surprising, therefore, if one some- 

 times encounters undescribed species. When such unnamed species are found, 

 particularly if they are of economic importance or are related to such forms, it 

 is highly desirable that they should be adequately described and named, and 

 the results published and made accessible. 



(2) The unknown organism may have been described and named in some 

 publication, but the description and name have been overlooked in the prepara- 

 tion of the Manual. Perhaps the description has been so inadequate or incom- 

 plete that it has not been possible to place it in a satisfactory classification. It 

 should be noted that the number of species that have been described is so great 

 that no one individual can know them all. Progress in classification comes about 

 largely as the result of the work of specialists in particular groups. Unfortunately 

 most groups of bacteria have not been adequately monographed. It is evidently 

 the function of a Manual such as this to draw largely upon the work of those 

 who have published monographs covering special groups of bacteria and to 

 supplement their achievements as far as possible by a necessarily less satisfactory 

 consideration of the unmonographed groups. It is clear that the fact that an 



